Projectile fuze capable of self-destruction



Feb. 4, 1969 c. N. WHELAN 3,425,352

PROJECTILE FUZE CAPABLE OF SELF-DESTRUCTION Filed Nov. 9, 1967 RNEYS United States Patent 3,425,352 PROJECTILE FUZE CAPABLE OF SELF-DESTRUCTION Charles N. Whelan, Potomac, Md., assignor to the United States of America as represented by the Secretary of the Army Filed Nov. 9, 1967, Ser. No. 681,665 US. Cl. 102-71 Int. Cl. F42c 9/00, 9/16 4 Claims ABSTRACT OF THE DISCLOSURE The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to me of any royalty thereon.

Background of the invention In the design of ground-to-air, ground-to-ground or airto-air projectiles a problem that must always be contended with is that should the projectile miss its intended target it might detonate in a friendly area. This problem is especially prevalent with those weapons that are employed in the direct support of ground troops in which danger is, of course, that the rounds will fall on the troops that are being defended. Modern warfare tactics demand a close integration of tanks, infantry and artillery for mutual protection, and this, of course, substantially increases the problem.

Prior attempts to arrive at a solution to this problem have centered around utilizing the spin-rate decrease of the fired projectile to permit the mechanical release of a cocked firing pin. This approach has a number of disadvantages. The spin decreases of approximately 200 r.p.s. are extremely difficult to sense, and a highly complicated mechanism is required to perform this function. As might be expected, these present designs require a number of small precision parts which are expensive and very difficult to manufacture. Furtherfi the requirement for a precision mechanism of this nature is often difficult to meet in wartime and many inaccuracies could be expected. Generally the prior art devices do not work well over the broad temperature range in which it is necessary for a military item to operate. The greatest difiiculty has been experienced in several designs at all temperatures below 0 F.

It is therefore an object of this invention to provide a projectile fuze capable of self-destruction which is of low cost and easy to manufacture.

It is a further object of this invention to provide a projectile fuze capable of self-destruction of improved reliability by eliminating moving parts.

' Still another object of this invention is to provide a projectile fuze capable of self-destruction with a long shelf life, unaffected by environmental condition, by eliminating the problems associated with preset stresses and fretting corrosion experienced by mechanical systems during storage or transportation.

Another object of this invention is to provide a projectile fuze capable of self-destruction which will operate "ice over a broad temperature range especially below temperatures of 0 F.

Summary of the invention The aforementioned and other objects are obtained by using a fuze which includes a pyrophorus material at the head of the delay train which will spontaneously ignite upon contact with the air. The pyrophorus material is exposed to air when a frangible cover over it is shattered upon firing the projectile. The pyrophorus material is used to initiate the remainder of the delay train. When the delay powder burning reaches the primer a detonation occurs which in turn initiates other units in the explosive train. Should the fuze hit a target prior to self-destruct initiation the nose will crush firing the primer causing the round to explode.

Brief description of the drawing The specific nature of the invention, as well as other objects, aspects, uses and advantages thereof, will clearly appear from the following description and from the ac- Description of the preferred embodiment In the drawing is shown a cross-sectional view of a projectile fuze 10 used on a 20 mm. projectile. The fuze 10 is formed by a shield 11 which is the nose of the fuze and the fuze body 21 which is joined to shield 11 at the forward end of the fuze body. Within shield 11 a breakable cover 13, such as glass, is placed directly on top of a quantity of pyrophorus material such as synthesized lithium dimethylamide. A standard delay powder unit 16 is placed directly adjacent to the pyrophorus material 15 forming the delay train. A primer 18 is positioned directly adjacent the delay train. The entire delay and primer assembly is placed within fuze 10 such that when a rotor 20 containing a detonator 22 rotates at the proper time detonator 22 will be in line with primer 18 and the projectile will be fired.

Operation of the self-destruct feature is commenced when the projectile is fired and the set back force shatters frangible cover 13, and the pyrophorus material 15 is exposed to air. It has been found that such materials e.g. synthesized lithium dimethyl-amide or a mixture of white phosphorous and carbon disulfide, will spontaneously ignite upon contact with air or, in particular, oxygen. The pyrophorus material 15 will then ignite a delay mix 16, which may be of the types well known to those skilled in the art, or it may be more pyrophorus material with an oxygenated compound added, such as aluminum oxide. Delay 'mix 16 will then require a few seconds to burn, and after the burning is completed primer 18 will be initiated. At this point rotor 20 will have placed detonator 22 in line with primer 18 so that when the primer is initiated the round will be exploded. Clearly, the fuze may be designed so that the time required for this self-destruct feature to operate will be such that the round will explode before the shell hits friendly areas having missed its target. If the fuze should hit its intended target prior to being initiated by the above-described self-destruct mechanism, the impact will crush shield 11, firing the primer 18, causing the round to explode.

The primary advantages of the above-described pyrotechnic delay-destruct system lie in the fact that the production costs of such a device will be low, and the device itself will be extremely reliable. The low cost of production is a result of the ease of assembly of my invention.

Devices such as this may be assembled by using common explosive assembly equipment coupled with inexpensive loading material. By eliminating all moving parts the reliability of the self-destruct feature has been substantially increased and the problems afliliated with preset stresses and fretting corrosion experienced by the prior art mechanical systems during storage or transportation are eliminated. The absence of moving parts also provides a system unaffected by gunfire acceleration forces. Further, the pyrotechnic device described herein will be substantially unaffected by environmental conditions such as temperature.

While my invention was described in the context of its use on a 20 mm. projectile, it will be apparent to those skilled in the art that the system will provide a self-destruct feature for any gun-fired projectile experiencing relative high G setback forces. It is contemplated that my invention can be used for other small caliber non-spin rounds which of course have had no self-destruct capability because the prior art devices required a spin signature.

I claim:

1. In a projectile fuze, :a means for self-destruction of a projectile, comprising:

(a) a quantity of pyrophorus material, said pyrophorus material being capable of being easily ignited upon exposure to air;

(b) a breakable cover adapted to be broken when said projectile is fired, said cover being placed so that said pyrophorus material will be exposed to air only when said cover breaks;

(c) a delay mix capable of producing a time delay by burning at a predetermined rate, said delay mix being placed so that it will be ignited by said pyrophorus material; and

(d) A primer means for causing initiation of the projectile adapted to be actuated when said delay mix has been consumed.

2. The means for self-destruction of a projectile of claim 1 in which said pyrophorus material is synthesized lithium dimethylamide.

3. The means for self-destruction of a projectile of claim 1 in which said pyrophorus material is a mixture of white phosphorous and carbon disulfide. v

4. The means for self-destruction of a projectile of claim 1 in which said delay mix is a pyrophorus material with an oxygenated compound added.

References Cited UNITED STATES PATENTS 4/1921 Chilowsky 10266 11/1960 Snelling 10266 X US. Cl. X.R. 10282 

